U.S. patent application number 09/953647 was filed with the patent office on 2002-01-24 for tire for heavy equipment.
This patent application is currently assigned to MICHELIN RECHERCHE ET TECHNIQUE S.A.. Invention is credited to Comps, Olivier, Giraud, Jacques, Palgen, Marie-Claude.
Application Number | 20020007894 09/953647 |
Document ID | / |
Family ID | 9543383 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020007894 |
Kind Code |
A1 |
Comps, Olivier ; et
al. |
January 24, 2002 |
Tire for heavy equipment
Abstract
A tire for heavy equipment, having at least one radial carcass
reinforcement surmounted radially to the outside by a crown
reinforcement formed of at least three so-called working plies
formed of inextensible metal cables, crossed from one ply to the
next, forming angles of between 15.degree. and 35.degree. with the
circumferential direction. At least one half-ply, formed of
inextensible metal cables and of width L', on either side of the
equatorial plane XX', is arranged between the edges of at least two
radially adjacent working plies, the cables of said half-ply
forming with the circumferential direction an angle, which is
firstly greater in absolute value than 25.degree., and secondly is
greater in absolute value than the largest angle formed by the
elements of the two working plies by an amount between 5.degree.
and 15.degree..
Inventors: |
Comps, Olivier;
(Clermont-Ferrand, FR) ; Giraud, Jacques;
(Beaumont, FR) ; Palgen, Marie-Claude; (Riom,
FR) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Assignee: |
MICHELIN RECHERCHE ET TECHNIQUE
S.A.
|
Family ID: |
9543383 |
Appl. No.: |
09/953647 |
Filed: |
September 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09953647 |
Sep 17, 2001 |
|
|
|
PCT/EP00/01669 |
Feb 28, 2000 |
|
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Current U.S.
Class: |
152/562 |
Current CPC
Class: |
B60C 9/2006 20130101;
Y10T 152/10765 20150115; B60C 9/2009 20130101; Y10T 152/10801
20150115; B60C 2009/2038 20130101; Y10T 152/10792 20150115; B60C
2009/2041 20130101 |
Class at
Publication: |
152/562 |
International
Class: |
B60C 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 1999 |
FR |
99/03416 |
Claims
We claim:
1. A tire for heavy equipment, comprising at least one radial
carcass reinforcement anchored within each bead to at least one
bead wire, forming an upturn, said reinforcement being surmounted
radially to the outside by a crown reinforcement formed of at least
three working plies formed of inextensible metal reinforcement
elements, which are parallel to each other within each ply and are
crossed from one ply to the next forming angles .alpha..sub.1,
.alpha..sub.2, .alpha..sub.3 of between 15.degree. and 35.degree.
with the circumferential direction, characterized in that the tire
further comprises at least one half-ply, formed of inextensible
metal reinforcement elements and of width L', on either side of the
equatorial plane XX', arranged radially between the edges of at
least two radially adjacent working plies, the axially outer and
inner ends of said half-ply being located, respectively, axially to
the outside of the end of the widest working ply and axially to the
inside of the end of the least wide working ply, at distances at
least equal to the amount L'/5, the reinforcement elements of said
half-ply forming with the circumferential direction an angle
.beta., which firstly is greater in absolute value than 25.degree.,
and secondly is greater in absolute value than the largest angle
formed by the elements of the two working plies by an amount
between 5.degree. and 15.degree..
2. A tire according to claim 1, characterized in that a half-ply is
arranged between the two working plies closest to the carcass
reinforcement.
3. A tire according to one of claim 1, characterized in that the
reinforcement elements of each half-ply are crossed with the
reinforcement elements of the working ply radially to the inside of
said half-ply and closest radially to the carcass reinforcement
1.
4. A tire according to claim 3, characterized in that the widths of
the working plies of the crown reinforcement are such that the ply
radially to the inside of each half-ply is less wide than the ply
radially to the outside of said half-ply.
5. A tire according to claim 4, characterized in that there are
present, on either side of the equatorial plane XX', two half-plies
arranged between the edges of two radially adjacent working plies
of the working reinforcement of three plies, the second half-ply
being formed of the same metal reinforcement elements as those of
the first half-ply, said elements of the second half-ply being
crossed with the elements of said first half-ply.
6. A tire according to claim 1, characterized in that the working
reinforcement is surmounted radially by a protective reinforcement
composed of two plies of elastic metal reinforcement elements, one
of said protective plies having an axial width greater than the
greatest axial width of the working plies.
7. A tire according to claim 6, characterized in that a ply of the
protective reinforcement has an axial width greater than the
greatest axial width of the working plies and is the radially inner
protective ply 51, whereas the width of the outer protective ply
has a width which lies between the largest two widths of the
working plies.
Description
BACKGROUND OF THE INVENTION
[0001] This is a continuation of pending PCT/EP00/01669, filed Feb.
28, 2000.
[0002] The invention relates to a tire having a radial carcass
reinforcement which is intended to be fitted on a heavy vehicle,
such as a transport vehicle or construction machinery. It relates
more particularly to the crown reinforcement of such a tire.
[0003] The prior art construction-vehicle tire shown in FIG. 1
comprises, as is known per se, a carcass reinforcement 1 composed
of a single ply of inextensible metal cables made of steel,
anchored within each bead to a bead wire 2 to form an upturn 10,
the end of which is substantially located at the level S.sub.0 of
the greatest axial width of the carcass reinforcement. Said carcass
reinforcement is radially surmounted by a layer 20 and profiled
members 21 of rubber mix, then by a crown reinforcement 3 composed
firstly of two plies 31 and 32 referred to as working plies and
secondly radially of two so-called protective plies 51 and 52. The
working plies are formed of inextensible metal cables made of
steel, which are parallel to each other within each ply 31, 32 and
are crossed from one ply 31 to the next 32, forming angles which
may be between 15.degree. and 45.degree. with the circumferential
direction. The axial widths of said working plies are generally
between 60% and 80% of the maximum axial width of the carcass
reinforcement 1. The protective plies 51, 52 are generally formed
of elastic metal cables made of steel, which are parallel to one
another within each ply 51, 52 and are crossed from one ply 51 to
the next 52, also forming angles which may be between 15.degree.
and 45.degree. with the circumferential direction. The widths of
said protective plies 51, 52 are usually less than the width of the
widest working ply. Finally, the cables of the radially outer
working ply 32 are usually crossed with the cables of the radially
inner protective ply 51. The crown reinforcement is itself
surmounted by a tread 4 which is joined to the two beads 7 by the
two sidewalls 6.
[0004] As is known, the crown reinforcements of radial tires, and
more particularly large-dimension tires, are subjected to great
deformation, which causes longitudinal and transverse shearing
stresses between the edges of two crossed plies (the longitudinal
shearing is greater than the transverse shearing when the cables of
crossed plies form small angles with the circumferential
direction), at the same time as a delamination stress, a radial
stress which tends to separate the edges of the two plies radially.
Said stresses are due first and foremost to the inflation pressure
of the tire, which means that the so-called belting pressure
between the carcass reinforcement and the crown reinforcement tends
to cause the circumferential expansion of said crown reinforcement;
next they are due to the load borne by the tire when travelling,
with a contact surface being produced between the ground and the
tire; then finally to the drifting of the tire when travelling.
Said shearing stresses generate fissures in the rubber mix
adjoining the end of the shortest ply, which fissures spread within
said mix and adversely affect the life of a crown reinforcement,
and therefore of the tire.
[0005] A clear improvement in the endurance was obtained by using
in the crown reinforcement at least one protective crown ply having
an axial width greater than the width of the axially widest working
ply.
[0006] Another solution, as noted in French Patent 2 421 742,
consists in more favourably distributing the stresses causing
separation between working crown plies, following the drifting of
the tire, by multiplying the number of working plies, for example
by using four working plies of reinforcement elements crossed from
one ply to the next, forming angles which may be between 15.degree.
and 35.degree. with the circumferential direction and by
distributing the reinforcement elements used in the conventional
two working plies on the four working plies such that the latter
each have the same thickness and the same rigidity in extension
measured perpendicular to the reinforcement elements of the
ply.
SUMMARY OF THE INVENTION
[0007] Multiplication of the working plies is not without its
drawbacks, particularly at the center of the reinforcement where
the number of plies has a very great influence on the flexural
strength of the crown of the tire. The invention proposes
increasing the resistance to separation between working plies of a
crown reinforcement having a widened protective ply plies and thus
to improve the endurance of such a crown reinforcement for a tire
for construction machinery, without increasing the number of
working plies at the center of the reinforcement.
[0008] The tire according to the invention, comprising at least one
radial carcass reinforcement anchored within each bead to at least
one bead wire, forming an upturn, said reinforcement being
surmounted radially to the outside by a crown reinforcement formed
of at least three so-called working plies formed of inextensible
metal reinforcement elements which are parallel to each other
within each ply and are crossed from one ply to the next, forming
angles .alpha., .alpha.' of between 15.degree. and 35.degree. with
the circumferential direction, is characterized in that at least
one half-ply, formed of inextensible metal reinforcement elements
and of width L', on either side of the equatorial plane, is
arranged radially between the edges of at least two radially
adjacent working plies, the axially outer and inner ends of said
half-ply being located, respectively, axially to the outside of the
end of the widest working ply and axially to the inside of the end
of the least wide working ply, at distances at least equal to the
amount L'/5, the reinforcement elements of said half-ply forming
with the circumferential direction an angle .beta., which is
firstly greater in absolute value than 25.degree., and secondly is
greater in absolute value than the largest angle formed by the
elements of the two working plies by an amount between 5.degree.
and 15.degree..
[0009] Preferably, a half-ply is arranged between the two working
plies closest to the carcass reinforcement. Whether there be one or
two half-plies, the reinforcement elements of each half-ply are
advantageously crossed with the reinforcement elements of the
working ply radially to the inside of said half-ply and closest
radially to the carcass reinforcement.
[0010] The widths of the working plies of the crown reinforcement,
which are generally unequal, are such that the working ply radially
to the inside of each half-ply is less wide than the ply radially
to the outside of said half-ply.
[0011] In the case of the presence, on either side of the
equatorial plane, of two half-plies arranged between the edges of
two radially adjacent working plies of the working reinforcement of
three plies, the second half-ply is formed of the same metal
reinforcement elements as those of the first half-ply, said
elements preferably being crossed with the elements of said first
half-ply.
[0012] The working ply, as is known per se, is surmounted radially
by a protective reinforcement composed of two plies of elastic
metal reinforcement elements. One of said protective plies,
preferably the radially inner ply, has an axial width greater than
the greatest axial width of the working plies, whereas the width of
the second protective ply has a width of a value which lies between
the values of the widths of the working plies.
[0013] The invention will be better understood with reference to
the following description, which refers to the drawings,
illustrating in non-limitative manner embodiments of the
invention.
DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a diagram, viewed in meridian section, of a
crown reinforcement for a construction-vehicle tire in accordance
with the prior art;
[0015] FIG. 2 shows a diagram, viewed in meridian section, of a
first variant of the crown reinforcement according to the
invention; and
[0016] FIG. 3 shows a diagram, still in meridian section, of a
second variant of a crown reinforcement according to the
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] The tire P according to the invention, the crown
reinforcement of which is shown in FIG. 2, is a tire for a
construction vehicle. Of large dimensions, the H/S form ratio of
said tire is equal to 0.80, H being the height of the tire on its
rim and S the maximum axial width of the tire, when the latter is
mounted on its operating rim and inflated to its recommended
pressure.
[0018] Said tire P comprises a radial carcass reinforcement
composed of a single ply 1 of inextensible metal cables, which is
anchored within each bead to at least one bead wire (not shown) to
form an upturn, the end of which is substantially located on the
straight line of greatest axial width of the carcass reinforcement,
which straight line is parallel to the axis of rotation. The
carcass ply 1 is surmounted radially, within its central part, by a
layer 20 of rubber mix and, in its lateral parts, by two triangular
profiled members 21 formed of the same rubber mix, said profiled
members making it possible to compensate for the differences in
meridian curvature between the carcass reinforcement and the crown
reinforcement. Radially to the outside of said layer and profiled
members, there is arranged a working crown reinforcement 3 and a
protective reinforcement 5.
[0019] The working reinforcement comprises first and foremost three
working plies 31, 32 and 33 which are axially continuous and of
widths L.sub.31, L.sub.32 and L.sub.33, respectively, the least
wide ply 31, in the case described, being radially closest to the
carcass reinforcement 1 and the widths L.sub.31, L.sub.32 and
L.sub.33 increasing radially from the inside to the outside. Said
three widths are equal to 0.5 S.sub.0, 0.55 S.sub.0 and 0.66
S.sub.0, respectively, So being the maximum axial width of the
carcass reinforcement (see FIG. 1). Said three plies 31, 32 and 33
are formed of inextensible metal cables, which are parallel to each
other in each ply and are crossed from one ply 31, 32 to the next
32, 33, forming angles .sub.1, .sub.2 and .sub.3 which are equal to
+18.degree., -24.degree. and +18.degree., respectively, with the
circumferential direction of the tire.
[0020] Radially between the edges of the least wide ply 31 and the
edges of the radially adjacent ply 32 of intermediate width, there
are arranged two half-plies 34, formed of the same inextensible
metal elements as those forming the plies 31, 32 and 33, said
elements being parallel to each other in each half-ply 34 and
crossed with the elements of the axially continuous ply 31 closest
to the carcass ply 1, forming with the circumferential direction an
angle .beta., greater than the angles .alpha..sub.1 and
.alpha..sub.2 and equal to -33.degree.. The axial width L' of each
half-ply 34 is equal to 0.33 S.sub.0. The axially inner end of the
half-ply 34 is located axially to the inside of the end of the ply
31 and at an axial distance from the equatorial plane XX', such
that the difference between the axial half-width of the least wide
working ply 31 and said distance is equal to 0.22 L', such that
there is an overlap between the axially inner edge of said half-ply
34 and the edge of the least wide axially continuous ply 31 which
is radially to the inside. As for the axially outer end of the
half-ply 34, it is axially to the outside of the end of the widest
ply 32 and at an axial distance from the equatorial plane XX', such
that the difference between said distance and the axial half-width
of the widest working ply 32 is equal to 0.37 L'.
[0021] The protective reinforcement, which finishes off the crown
reinforcement and, radially to the outside of the working
reinforcement described above, is formed of two plies 51 and 52 of
elastic steel cables. Cables which, under a tensile force equal to
the breaking load, have a relative elongation of at least 4% are
referred to as elastic, whereas cables are referred to as
inextensible when their relative elongation, measured at 10% of the
breaking force, is less than 0.2%. The cables of said two plies are
crossed from one ply 51 to the next 52, forming angles respectively
equal to -24.degree. and +24.degree. with the circumferential
direction, the cables of the protective ply 51 closest to the
carcass reinforcement being crossed with the cables of the working
ply 33 farthest from said carcass reinforcement. The axial width
L.sub.51 of the ply 51 is very much greater than the width L.sub.33
of the widest working ply, and its end is axially to the outside of
the axially outer end of the half-ply 34, such that said protective
ply 51 axially covers all the working plies and inserted
half-plies. The width L.sub.52 of the second protective ply is
substantially equal to half the total of the widths L.sub.32 and
L.sub.33 of the two widest working plies.
[0022] FIG. 3 shows a variant of a crown reinforcement comprising
two half-plies 34, respectively, located between the working plies
31 and 32 and between the working plies 32 and 33, said working
plies 31, 32, 33 being in all respects identical to the plies
described above. The same applies for the first half-ply 34
relative to the half-ply of FIG. 2. As for the second half-ply 34,
between the working plies 32 and 33, it is formed of cables
identical to those of the first half-ply which form an angle .beta.
of 33.degree. with the circumferential direction, but are crossed
with the cables of the first half-ply 34. As for its axial width,
it obeys the principles set forth above, with the exception, as is
known per se, of not having two ends of a ply in the same parallel
plane.
* * * * *